According to a study from researchers at Carnegie Mellon University, wind …

If we want to obtain 20 percent of our electricity from wind power by 2030, the US is going to need at least 50 gigawatts from offshore wind farms, according to the US Department of Energy. The National Renewable Energy Laboratory (NREL) estimated that this wouldn’t be a problem—we could provide four times our 2010 electricity generation capacity with offshore wind power alone. The US hasn’t actually built any offshore wind farms yet, although there are at least 20 in the planning stages.

As part of that planning, the Interior Department recently performed a review, concluding there would be no significant environmental or socioeconomic impacts from wind farms off the mid-Atlantic Coast. However, according to a paper published today in the Proceedings of the National Academies of Science, we should be worrying the converse: the impact of the environment on the wind farms, from hurricanes in particular. In certain risky offshore regions off the Atlantic and Gulf Coasts, there is a high probability that at least one turbine would be destroyed by hurricanes within 20 years, and a smaller chance that half the turbines in a farm would be wiped out.

The authors of the paper, a group from Carnegie Mellon, used a probabilistic model to estimate the number of turbines destroyed by a hurricane. They performed this analysis for four locations where either farm leases have already been signed or projects have been proposed: Galveston County, TX; Dare County, NC; Atlantic County, NJ; and Dukes County, MA. The differences in location affect the probability of hurricane occurrence and the maximum wind speed, which were obtained using historical data.

Turbines are at risk from hurricanes due to the high maximum wind speeds, which exceed the design limits and can cause blade loss and tower buckling. In 2003, two typhoons (Maemi and Dujuan) destroyed turbines in Japan and China.

It’s all in the yaw

In the current study, the researchers only considered buckling, since blades can be more easily replaced. The buckling is much more likely when the turbines cannot yaw, or turn into the direction of the wind. Most modern turbines have this ability, since it allows them to generate more power. Somewhat ironically, however, hurricanes usually knock out the external power necessary for yaw motors. Even with power, winds in a hurricane can change direction faster than the turbine can yaw.

Initially, the team looked at a 50 turbine farm and calculated how many turbines would be destroyed if the farm was hit by a single hurricane, assuming the turbines couldn’t yaw. If the farm encountered a Category 3 hurricane, meaning wind speeds at least 45 meters per second, up to 6 percent of the turbines could buckle. A Category 4 hurricane, with wind speeds at least 50 m/s, could buckle nearly half of the farm. For some perspective, every state on the Gulf of Mexico and nine of the 14 on the Atlantic coast has been hit by Category 3 or higher hurricanes since 1856.

Next, they calculated the probability of turbine buckling in the four specific locations over a period of 20 years. In this case, they performed separate analyses of turbines that could and could not yaw.

The team found that Galveston and Dare Counties are the riskiest locations (of the four considered) for offshore wind farms. In Galveston County, without the ability to yaw, there is a 60 percent probability that at least one turbine tower would buckle in 20 years, and 30 percent chance that half the farm would be destroyed. Dare County is little better, with the same 60 percent chance for one turbine and 9 percent for more than half.

Atlantic and Dukes counties, on the other hand, were much safer. Without the ability to yaw, there was a 15 percent probability in Atlantic and 10 percent probability in Dukes that at least one turbine would buckle in the 20 year period. In both locations, there was a less than one percent probability that more than half the farm would buckle.

Giving turbines the ability to yaw significantly decreases the probability of buckling. The chances of a single turbine buckling in Galveston and Dare Counties drop to 25 percent and 15 percent, and the probabilities of more than half the farm being destroyed drop to 10 percent and less than one percent, respectively.

If the turbines in Atlantic and Dukes Counties can yaw, there is little chance that even a single turbine would be destroyed in the 20 year period.

Further emphasizing the importance of yaw, the researchers found that without yaw, there is a one in ten chance that an entire 50 turbine farm could be destroyed in Galveston County.

What can we do?

The authors suggest three reasonable ways to avoid hurricane damage: 1) increase the maximum wind speed that designs can handle; 2) make sure the turbine can quickly turn into the direction of rapidly changing winds; and 3) build most offshore wind farms in areas with lower risk.

Most modern turbines are rated to withstand maximum wind speeds of around 42 m/s. These designs are typically based on conditions in northern Europe and the North Sea, the location of most existing offshore wind farms. Some estimates put the cost of increasing the safety factor at 20-30 percent for turbines on land, but the fraction would likely be smaller for offshore turbines. Most of the cost there goes into transportation, installation, and maintenance, rather than the construction of the turbine itself.

Adding battery backups for yaw motors could add up to $40,000 to the turbine cost and a metric ton (literally) to the weight. But allowing a turbine to yaw during a hurricane significantly reduces the probability of buckling. In the safer locations, this risk is practically eliminated when the turbines can yaw. Batteries could potentially buffer the farm’s power output when the weather isn’t threatening.

There are a couple limitations of this study. The authors emphasize that the results in their paper do not represent all possible offshore wind farm locations—hurricane occurrence and intensity vary wildly from location to location. In addition, the entire analysis is based on historic data. Any predictions would be thrown off if climate change affects hurricane behavior, and the relationship here is unclear at best.

In fact, there is a good chance the probabilities presented here are underestimates. The model only considered tower buckling, but falling blades can also destroy the turbine. In addition, the buckling analysis didn’t account for the forces of heavy waves, another common occurrence during hurricanes.

This type of analysis could potentially be performed as part of a potential offshore wind site evaluation. Even without redesigning turbines to withstand higher winds, simply avoiding more dangerous locations could reduce the risk of turbine damage significantly.

Kyle Niemeyer
Kyle is a science writer for Ars Technica. He is a postdoctoral scholar at Oregon State University and has a Ph.D. in mechanical engineering from Case Western Reserve University. Kyle's research focuses on combustion modeling. Emailkyleniemeyer.ars@gmail.com//Twitter@kyle_niemeyer

109 Reader Comments

The authors suggest three reasonable ways to avoid hurricane damage: 1) increase the maximum wind speed that designs can handle; 2) make sure the turbine can quickly turn into the direction of rapidly changing winds; and 3) build most offshore wind farms in areas with lower risk.

The authors suggest three reasonable ways to avoid hurricane damage: 1) increase the maximum wind speed that designs can handle; 2) make sure the turbine can quickly turn into the direction of rapidly changing winds; and 3) build most offshore wind farms in areas with lower risk.

So we might lose a turbine per field every two decades? I guess I don't see the reason to call in the cavalry just yet. When the storm is done go in and fix/replace it. I'll still rest a lot easier than losing cooling water or backup power to the South Texas Project. Speaking of which, have they finally managed to get Unit #2 up and running again after the last refueling screw-up in November?

Could it possibly be cost effective to make the turbines submersible? Perhaps, pull the plug and submerge it when a major hurricane approaches. Afterwards send a diver out to replace the plug and re-float it.

Or maybe make them so that when in danger of catastrophic failure the blades all detach simultaneously. Maybe put a beacon on each blade so they can be located and reattached/recycled when the weather clears.

Could it possibly be cost effective to make the turbines submersible? Perhaps, pull the plug and submerge it when a major hurricane approaches. Afterwards send a diver out to replace the plug and re-float it.

Or maybe make them so that when in danger of catastrophic failure the blades all detach simultaneously. Maybe put a beacon on each blade so they can be located and reattached/recycled when the weather clears.

I live in Palm Beach county Florida & keep hearing about a sugarland windfarm that some company is working on getting off the ground putting wind turbines in land leased from sugar farmers somewhere in the county. It recently got approval or something I think.

Could it possibly be cost effective to make the turbines submersible? Perhaps, pull the plug and submerge it when a major hurricane approaches. Afterwards send a diver out to replace the plug and re-float it.

probably not, since those things are like 80m tall (not including blades!) and this article says current technology only allows them to be built at a depth of 20-30m because they need to be anchored to the seabed.

Could it possibly be cost effective to make the turbines submersible? Perhaps, pull the plug and submerge it when a major hurricane approaches. Afterwards send a diver out to replace the plug and re-float it.

Or maybe make them so that when in danger of catastrophic failure the blades all detach simultaneously. Maybe put a beacon on each blade so they can be located and reattached/recycled when the weather clears.

I thought the alternate idea to wind farms at sea was large paddles under water that would wax/wane with the waves, collecting that energy under within the ocean. Granted, those things, too, would have some sort of max stress they could withstand. But, if they were designed to handle getting pushed back-n-forth by the ocean instead of air, then perhaps they could hand a hurricane a bit better.

What are other options? Weren't fuel cells supposed to be all the rage soon?

I'd prefer instead of focusing on large-scale solutions, folks focus on local / personal energy solutions. But those are still priced so high it's sort of a non-option unless you want to be an eco-nazi.

Could it possibly be cost effective to make the turbines submersible? Perhaps, pull the plug and submerge it when a major hurricane approaches. Afterwards send a diver out to replace the plug and re-float it.

Or maybe make them so that when in danger of catastrophic failure the blades all detach simultaneously. Maybe put a beacon on each blade so they can be located and reattached/recycled when the weather clears.

The moment the turbine blades hit the water they'd come apart in a spectacular fashion and you'd have shrapnel flying everywhere. You'd need to feather them first.... 20 tons of them... in hurricane winds. Not sure if it can be done. Maybe a few days in advance?

Detaching the blades would make for some awesome 20 ton projectiles.

Anyway, with both ideas, if they caused damage due to a hurricane: accident covered by insurance. If they caused damage due to operator action: negligence lawsuit.

So we might lose a turbine per field every two decades? I guess I don't see the reason to call in the cavalry just yet. When the storm is done go in and fix/replace it. I'll still rest a lot easier than losing cooling water or backup power to the South Texas Project. Speaking of which, have they finally managed to get Unit #2 up and running again after the last refueling screw-up in November?

That's enough to wreck the economics of it... Each turbine costs $3-5 million, so if you have to price in the cost of replacing 50% of your wind farm when a big hurricane comes through, it may be cheaper to build the wind farm elsewhere (even if that location has less wind.)

I can see why the gulf coast is so attractive for wind farms; you won't get many people crying because "it ruins our view" because the gulf coast is just flat out ugly... swamps, wetlands, muddy beaches filled with garbage and plenty of mosquitos. Galveston especially; the town was basically wiped off the map by a big hurricane in 2007 so they're probably hurting for money.

It seems like there is plenty of kinetic energy available for use during a hurricane. Why is a $40,000 battery needed? Couldn't you make it have a mechanical failsafe yaw? Essentially make a blade assisted wind vane.

There is a fourth way to address this- just replace broken turbines if/when they break and eat the cost. It sounds like it may be cheaper to do this than to beef up the design or add battery backup. It may actually be a bit more environmentally sound to just let the unit fail compared to the possibility of having a ton of lead/acid backup batteries at the bottom of the ocean (or 50 tons if the whole farm goes down....).

Making these devices capable of withstanding hurricane force winds AND capturing a lot of energy from them would have the side benefit of pulling energy out of the storm and reducing its strength. If there were any way to also store that energy for later use, that would be yet another benefit.

Could it possibly be cost effective to make the turbines submersible? Perhaps, pull the plug and submerge it when a major hurricane approaches. Afterwards send a diver out to replace the plug and re-float it.

I can see why the gulf coast is so attractive for wind farms; you won't get many people crying because "it ruins our view" because the gulf coast is just flat out ugly... swamps, wetlands, muddy beaches filled with garbage and plenty of mosquitos.

You know, some of us actually do find beauty in the unique biodiversity of our wetlands.

That being said, a wind farm in the background wouldn't bother me at all.

I bet the risks are plenty higher than this estimate. Before it happened, how likely did people figure that a tsunami would mess up the Japanese reactor as bad as it did?

I'm not saying we shouldn't build, I'm not that risk averse, but nature has a history of "thinking outside the box" when it comes to destroying things. Our models don't always catch the most likely failure modes, but experience helps us fix that. We can build them anyhow and see how it goes.

I thought the alternate idea to wind farms at sea was large paddles under water that would wax/wane with the waves, collecting that energy under within the ocean. Granted, those things, too, would have some sort of max stress they could withstand. But, if they were designed to handle getting pushed back-n-forth by the ocean instead of air, then perhaps they could hand a hurricane a bit better.

Paddles as such won't work in the open ocean because surface wave disturbances decay exponentially with depth. There are various schemes to have bendy joint contraptions or oscillating water columns to extract energy directly at the surface, but then you incur some of the same risks due to dynamic range of the operating regime.

Paddles or concentrators below the surface can work where there are significant flows, e.g., tidal or channel flows.

Never understood people that complain about Wind Turbines "destroying the view". Personally I think they are pretty graceful (for man-made buildings) and certainly don't intrude that much on any natural beauty of a given location. Also if you care that much turn and look the other way...

Clearly I misunderstand something. Why can't the output of a turbine be used to yaw the tower? Also, does this assume state of the art pitch-control on the blades? It otherwise sounds like an incredible engineering challenge to improve the maximum wind gust a current tower can withstand. Maybe some sort of wind-break at the edges of the farm that can be raised and lowered?

I need to read the study itself, but the article seems to imply that this study applies to horizontal axis wind turbines (thus the need for yaw motors). I wonder if vertical axis turbines are more forgiving to these sorts of conditions?

I realize that vertical axis turbines, particularly large ones, may have issues of their own (which is likely why all large turbines to date have been horizontal axis designs). But, it seems possible that economics might push for their development in regions where losing your horizontal axis turbine to extreme weather is likely.

In any case, it appears that this study would indicate that new designs will have to be considered in order to make wind turbines economical in severe weather areas.

Clearly I misunderstand something. Why can't the output of a turbine be used to yaw the tower? Also, does this assume state of the art pitch-control on the blades? It otherwise sounds like an incredible engineering challenge to improve the maximum wind gust a current tower can withstand. Maybe some sort of wind-break at the edges of the farm that can be raised and lowered?

You might envision the following scenario: as the hurricane approaches and wind speeds build, the turbine is yawed to track the wind. Eventually, the pitch control must be used to effectively deactivate the turbine. Then the winds shift (as they always do during a hurricane). At this point you will need external power (or backup) to maintain alignment.

What is the price per GW on these things? Wouldnt it be less risky to build more generation III+ nuclear stations instead of thousands of these wind turbines that could potentially be destroyed by hurricanes?

What is the price per GW on these things? Wouldnt it be less risky to build more generation III+ nuclear stations instead of thousands of these wind turbines that could potentially be destroyed by hurricanes?

Sure. If you want to wait 20-30 years for the plants to be built - and don'tmind the risk of some other natural disaster taking one of them out?

All construction is at risk of natural forces - the solution is always the same, build where the risk is smallest.

Could it possibly be cost effective to make the turbines submersible? Perhaps, pull the plug and submerge it when a major hurricane approaches. Afterwards send a diver out to replace the plug and re-float it.

Or maybe make them so that when in danger of catastrophic failure the blades all detach simultaneously. Maybe put a beacon on each blade so they can be located and reattached/recycled when the weather clears.

What if the blades could be designed to be retractable, or collapsible? It could be done remotely, or have some sort of switch that when the wind speed reaches XXX MPH, the blades automatically collapse or retract.

What if the blades could be designed to be retractable, or collapsible? It could be done remotely, or have some sort of switch that when the wind speed reaches XXX MPH, the blades automatically collapse or retract.

Presumably constructing them like that would likely make them:1) More expensive2) More fragile (joints and fittings)

Could still be worth it, but I don't know the cost/benefit analysis there...

Obviously everything has a design limit, and turbines must spin under control so as to not fly apart and become spinning wheels of death (TM, Apple). Replacing destroyed units is always an option, but that only works if we have alternative generation ready to back-fill the lost supply. Imagine losing several hundred MW of wind power during a late summer heat wave. The East coast already runs at the edge of supply in the summer as it is. Hopefully "alternative energy" can grow faster than the mortality rate of coal and can be as reliable.

Besides, isn't pretty much the entire East coast and gulf region in a hurricane zone? Where exactly could they be put and still be part of American soil?

I don't understand why the turbine needs a battery weighing one metric ton to permit yaw. The turbines are connected to the electricity grid; why can't the turbine draw power from the grid if it needs to turn? I'm sure the people running the grid can organise sufficient supply for the week. If you really need a battery (?!) you could have one larger battery shared across the whole farm -- tat way you can limit the potential environmental affect because you will only need to get one off the seabed. Also, I note that vertical axis wind turbines do not need to yaw, so the authors of the paper made assumptions about the technology being deployed in the area. The article seems to raise Big Issues which have fairly simple solutions. Was the research commissioned by the oil industry?

Also, I note that vertical axis wind turbines do not need to yaw, so the authors of the paper made assumptions about the technology being deployed in the area. The article seems to raise Big Issues which have fairly simple solutions. Was the research commissioned by the oil industry?

There are no large scale commercial offshore VAWT, so it's a moot point for the foreseeable future, but VAWT would probably experience just as many problems at such wind speeds.

Also, a study like this much more useful for the backers of the wind farms since it allows for reasonable projections of damages in order to obtain insurance at acceptable rates.

Hmm. All modern wind turbines can feather their blades (i.e., rotate the blades so the wind blows through and doesn't turn them). They already do tjis at high wind speeds to avoid damage. Need to look at their study to see why that wouldn't do the trick here.

Interesting. I'm at least happy to see that proper research (even if as researchers admit it may be somewhat limited) being done on the matter. What a disaster we could face if off shore wind farms were just placed where we could get permits/support the fastest.

I personally think more research is needed on exactly what happens to a turbine in a hurricane. Most likely use scale experiments or computer modeling. We could study the stress points and even maybe experiment with the idea of adding backup power and the ability to yaw. I think a few years of good R&D focusing specifically on the effects of hurricanes on wind turbines we may be able to come up with something great and almost (lets say 80-90% maybe) hurricane proof.

I can see why the gulf coast is so attractive for wind farms; you won't get many people crying because "it ruins our view" because the gulf coast is just flat out ugly... swamps, wetlands, muddy beaches filled with garbage and plenty of mosquitos. Galveston especially; the town was basically wiped off the map by a big hurricane in 2007 so they're probably hurting for money.

I don't think it's possible to know anything about it and still make comments like that.

It was not "wiped off the map," and it is not "hurting for money" — at least no more than any other municipality.

Mosquitoes are a fact of life in any coastal region, and Texas beaches are really quite clean, thanks to the work of a lot of people who care. And it's not swamps so much as breezy fields of sand and grasses, although there are wetlands and coastal marshes; in any case, beauty and the eye of the beholder.

The point is, it would be enough to tell you to quit your badmouth trolling, but I can't let stand such baseless trashing of someplace I and many others know and love well.

I'd much rather see windmills along the ocean horizon than oil platforms, but until we pump it dry, the gulf you find so ugly is busy powering your vehicles and yielding plastics for your gadgets, and people who live and work here who make it possible do so tirelessly, with or without your gratitude.

And no matter how many go, they will do less damage and cost less to repair than one nuclear incident. I actually find it quite amazing how much thought and research is going into this, given that it really isn't that big a deal if one of them does happen to go.